1. Field of the Invention
The subject of the present invention is a device allowing the effective volumetric displacement and/or the effective volumetric ratio of a piston engine to be varied while it is running.
2. Background of the Invention and Related Art
The volumetric displacement of an engine usually denotes the geometric characteristics of said engine defined by the bore and the stroke. Here, we shall adopt the idea of effective volumetric displacement represented by the volume of gas at atmospheric pressure actually retained by the engine in order to perform each cycle.
In conventional parlance the volumetric ratio is also a geometric relationship between the volume of the chamber and the volume defined by the stroke multiplied by the bore. Here we shall adopt the effective volumetric ratio determined by the effective compression ratio of the fresh gases.
Maximum performance in internal combustion piston engines is generally recorded at full load, that is to say at wide-open throttle at the speed or range of speeds at which the mean effective pressure of the engine cycle is at its maximum value.
For each engine, these operating conditions correspond to a defined power and a defined speed. What this amounts to is that as soon as the work demanded of an engine no longer corresponds to these power and speed conditions, its performance drops.
The main characteristic of engines which defines the power and speed at which maximum performance is found is their volumetric displacement.
In everyday use, particularly in the field of motor vehicles, the engine operating conditions which give rise to optimal performance are rarely united. This is because the volumetric displacement of engines is constant and the power demanded of them by the driver varies considerably.
In general practice, the further the working conditions imposed on the engine by the driver are from its maximum-performance conditions, the poorer its performance.
In low-power use, for example when travelling through town, for the same amount of work, engines with a large volumetric displacement consume more energy than engines with a large volumetric displacement [sic], because they are operating further from their maximum-performance operating conditions. The drawbacks of engines with a large volumetric displacement may become an advantage when the conditions of use require high power, for example on high-speed freeways.
In any event, engine power is altered mainly by changing their speed using a gearbox and changing their load using the throttle which controls the inlet pressure by throttling and modifies the degree of filling of the cylinder(s) and the mean effective pressure for the engine cycle.
Another characteristic of engines determines their overall performance and this is their volumetric ratio. The latter is defined by the relationship between the volume of the cylinder and the volume of the combustion chamber. This ratio is fixed and is calculated to take account of the maximum load conditions of the engine and of the fuel used although at part load, or when the cylinder is insufficiently filled at high speeds, this ratio could be significantly increased in order to improve engine performance.
While the advantage of adapting the volumetric displacements of engines to suit the work demanded of them is clear, their is currently practically no effective device which allows engines, particularly motor vehicle engines, to achieve this result.
Experiments have, however, been performed on devices which, in particular, envisage disengaging or passivating a number of cylinders on multicylinder engines.
None of these devices, on account of the impracticalities of implementing them and of their relative effectiveness, has been considered worthy of being produced in any number.
While it is advantageous, in order to maintain optimum performance, for the volumetric ratio of engines to be adapted to suit the filling of their cylinder(s), particularly at high speeds, no device yet provides a relevant solution for obtaining such a result.
It is to significantly improve the overall performance of internal combustion piston engines, given the varying context in which they are used, that the device according to the invention envisages that any engine equipped therewith should exhibit specific features which distinguish it from an engine as defined according to the rules of the prior art.
The invention therefore provides for a device for varying an effective volumetric displacement and/or an effective volumetric ratio of an engine which comprises a piston and a cylinder, the device comprising a first device for controlling the effective volumetric ratio of the engine by modifying a starting point of a stroke of the piston with respect to the cylinder, and a second device for controlling the effective volumetric displacement of the engine by discharging into an inlet pipe excess gases let into the cylinder of the engine. The first device may be adapted for controlling the effective volumetric ratio of the engine without modifying a length of the stroke. The first device may be adapted to adjusting the length of a piston upstroke. The first device may comprise a system of gears. The system of gears may comprises a first rack arranged on a lower part of the piston, the rack being held in a guide system which allows the rack to move longitudinally, and a second rack disposed in an engine block of the engine, the second rack being movably longitudinally. The system of gears may further comprise a device for controlling the position of the second rack, and a gear mounted on a connecting rod which is coupled to a crankshaft. The gear may be positioned between the first and second racks.
The second device may further comprise an additional inlet valve, and a device for controlling the opening and closing of the inlet valve. The device for controlling the opening and closing of the additional inlet valve may be adapted to modify an angular offset of a point at which the inlet valve opens and closes. The second device may comprise a device for controlling the opening and closing of an intake valve. The device for controlling the opening and closing of the intake valve may be adapted to modify an angular offset of a point at which the intake valve opens and closes. The device which controls the opening and closing of the additional inlet valve may comprise a camshaft which is coupled to a device which controls an angular offset with respect to a crankshaft. The device which controls the opening and closing of the intake valve may comprise an additional camshaft coupled to a device which controls an angular offset with respect to a crankshaft. The additional camshaft may be coupled to the intake valve via a mechanical linkage. The device for controlling the opening and closing of the inlet valve may further comprise a movable intermediate pulley. The device for controlling the opening and closing of the inlet valve may comprise an intermediate pulley and one of a timing belt or a timing chain, and wherein the intermediate pulley which adjusts a length of one of the timing belt or the timing chain.
The device may further comprise a device which controls a position of the second rack. The device which controls a position of the second rack may comprise an actuator. The actuator may comprise a hydraulic actuator which is coupled to the second rack via a mechanical linkage. The device for controlling the opening and closing of the inlet valve may comprise an actuator which controls the position of the intermediate pulley. The actuator may comprise a hydraulic actuator. The gear may have a truncated profile. The gear may have teeth which transmit movement between the piston and the connecting rod. The gear may be constantly centered between the first and second racks. The piston may comprise a shortened piston having piston rings and no piston skirt.
The first device may comprise a hydraulic actuator comprising a rod and an actuator piston, the hydraulic actuator being adapted to maintain a volume of fluid displaced as a function of a stroke of the actuator piston. The device may further comprise a control mechanism adapted to allow the rod to be displaced into a determined position or kept in a determined position with respect to a body of the hydraulic actuator. The first device may comprise a hydraulic actuator mounted on a block of the engine, wherein the hydraulic actuator further comprises an actuator cover, an actuator piston, an actuator rod, and an actuator rod extender. The hydraulic actuator may be adapted to move the second rack longitudinally. The hydraulic actuator may further comprise a control mechanism utilizing a control rod having a shoulder and being movable longitudinally, the control rod being positioned parallel to the actuator rod and passing through the actuator cover, the actuator body and the actuator piston via orifices formed in the actuator cover, actuator body and actuator piston. The hydraulic actuator may further comprise at least two valves housed in a duct and disposed longitudinally and eccentrically and formed in the actuator piston, the at least two valves being adapted to allow or prevent a flow of hydraulic fluid between an actuator upper chamber and an actuator lower chamber. The at least two valves may include rings which can slide around the control rod, wherein the rings have an inside diameter which is smaller than a diameter of the shoulder of the control rod, and wherein hydraulic actuator further comprises a nonreturn valve which is housed in a hydraulic-fluid inlet duct. The actuator piston may have a cavity on a cylindrical surface facing an orifice of the hydraulic-fluid inlet duct opening into a central part of the actuator body, the cavity being of a height at least equivalent to a maximum stroke of the actuator piston and being connected to the duct disposed longitudinally and eccentrically and formed in the actuator piston connecting upper and lower circular surfaces of the actuator piston, via a connecting passage. The nonreturn valve may comprise a ball held on a seating surface by a spring, wherein the ball is adapted to close an orifice. The orifice which opens into the central part of the actuator body may be connected to a pressurized hydraulic circuit which lubricates the engine. The hydraulic actuator may comprise rubber O-ring seals. The shoulder of the control rod may center the control rod in the eccentric longitudinal duct formed in the actuator piston, the shoulder having one of grooves or slots for allowing fluid to flow along the duct.
The invention also provides for a device for controlling the volumetric ratio of an engine which comprises an engine block, a piston, a cylinder, and a connecting rod, the device comprising a first rack comprising teeth and being coupled to the piston, a second rack comprising teeth and being movable with respect to the engine block, a device for moving the second rack, and a gear comprising teeth and being movably mounted to the connecting rod, wherein the teeth of the gear are adapted to engage the teeth of each of the first and second racks.
Thus, the device according to the invention, in a particular embodiment, displays the following advantages:
In order to remain at optimum performance, the engine automatically adapts its volumetric displacement to the work demanded of it, taking account of the speed conditions imposed on it.
When associated with a supercharging device, the engine may be of a smaller size than a conventional engine while at the same time maintaining a high power, and this may be achieved without detriment to the performance at part load.
When its cylinder(s) is(are) poorly filled, particularly at high speed, the engine adapts its volumetric ratio to said filling conditions in order to optimize its performance, i.e. it optimizes its effective compression ratio according to the speed.
The maximum power of the engine is increased particularly by improving the filling of its cylinder(s) at high speed.
The engine performance is increased significantly over most of its power range.
The maximum performance of the engine may be obtained over a broader speed range.
The pumping losses are reduced over most of the engine power range.
The low idle speed can be lowered thanks to the reduction in residual burnt gases.
The engine can run with downgraded performance to allow the catalytic converter used in the exhaust for treating pollutants to be heated up quickly.
Piston/cylinder friction is reduced by virtue of the method for guiding the piston longitudinally.
The speed has less of an effect on the friction.
The mechanical parts are particularly compact and their speed, with the exception of that of the piston, is low.
The ovalization of the cylinder(s) through wear is reduced because of the absence of side thrust on the piston due to the obliqueness of the connecting rod.
Furthermore, the device according to the invention in particular envisages that:
At low volumetric displacement, the engine cycle will use an expansion stroke which is longer than the stroke used to compress the gases, the expansion diagram then being cut off later than on an engine as defined in the prior art and with the same volumetric displacement.
At low volumetric displacement, the time needed to compress the gases is shorter, and this limits the time that the gases spend confined and is of benefit with regard to the initiation of undesirable detonation effects.
To achieve these results, the device according to the invention comprises, according to a first characteristic:
A system for controlling the volumetric ratio of the engine while it is running. The system works by modifying the starting point of the piston travel with respect to the cylinder without modifying the length of said stroke.
A system for controlling the effective volumetric displacement of the engine. The system works by discharging into the inlet pipe some of the gases let into the cylinder of the engine by the participation of an additional inlet valve. During operation with reduced volumetric displacement, closure of the additional inlet valve can be retarded significantly so that during its upstroke in the cylinder the piston discharges the excess gases let in and so that the start of compression of the gases takes place later in the upstroke of the piston. According to an alternative form of the device according to the invention, the inlet valve as defined according to the prior art may itself be used for this task, by controlling its opening and closing diagrams.
This device according to the invention comprises, in particular, for one cylinder:
A piston equipped with a rack mounted as an integral part of its lower part, said rack constituting one of the parts of a gearing system and being held in a guide system which allows it a longitudinal translational movement.
A control rack mounted in a cavity or on a guide formed in the engine block which allow it a longitudinal translational movement, the position of said control rack being controlled by a control device.
A connecting rod mounted freely on the engine crankshaft which, at its upper part, has a freely mounted gear, said gear constituting the element which transmits movement between the piston and said connecting rod.
An additional inlet valve, whose camshaft, which controls its opening/closure, is slaved to a device which controls its angular offset with respect to the engine crankshaft, this making it possible to modify the angular offset of the point at which said valve closes and opens with respect to the crankshaft.
According to one particular embodiment, its operation requires:
Probes transmitting various engine operating parameters;
One or more computers or devices which process said parameters;
A control device which allows the position of the control rack to be altered according to the result of the processing of the parameters from said probes;
A slaving device which allows the angular offset of the camshaft controlling the opening of the additional inlet valve to be altered according to the result of the processing of the parameters from said probes.
Finally, the device according to the invention comprises:
A piston which, in its lower part, is integral with a rack and which fulfills the same function as the piston of any engine as defined according to the rules of the prior art. The only difference is the way in which movement is mechanically transmitted to the crankshaft;
A connecting rod mounted freely on the crankshaft which fulfills the same function as the connecting rod of any engine as defined according to the rules of the prior art. The only difference is the way in which it is mechanically connected to the piston;
A gear mounted freely at the upper end of the connecting rod and which is slaved to the movement of the piston via the gearing system which it forms with the rack integral with the lower part of said piston, on the one hand, and with the control rack mounted in a cavity or on a guide, formed in the engine block and held in position by its control device, on the other hand. The gear is designed to form the member which transmits movement between the piston and the connecting rod;
A control device which allows the position of the control rack to be altered, and which comprises:
At least one hydraulic actuator or any other system which allows a translational movement to be imparted to the control rack and which is secured to said control rack by any mechanical linkage whatsoever;
At least one hydraulic actuator or any other system capable of forming a device which controls the angular offset of the camshaft which controls the opening of the additional inlet valve, it being possible for said hydraulic actuator, according to a particular embodiment and by way of nonlimiting example, to alter the position of an additional pulley thus varying the length of belt or chain between the pulley of the camshaft of the engine inlet and exhaust valves as defined in the prior art, and the pulley of the camshaft of the additional inlet valve;
And a device which controls the angular offset of the camshaft controlling the opening of the additional inlet valve and which does not necessarily act on the camshaft controlling the engine inlet and exhaust valves as defined according to the rules of the prior art.
In order to minimize the cost of producing an engine with variable volumetric displacement and to minimize the power consumption of the control device making it possible to alter the position of the control rack, this control device, according to a particular embodiment, displays the following advantages:
The control rack is moved and constantly kept in the desired position without the use of a hydraulic pump;
The position of the control rack and therefore the volume of the engine combustion chamber may be controlled using a very low-power slaving device;
Any transfer of hydraulic fluid needed for any change in position of the control rack is performed without the use of an auxiliary hydraulic pump. According to the invention, the hydraulic actuator used to perform any change in position of said control rack itself performs said transfers and in order to do so makes use of the constant changes in the direction of the force to which it is subjected;
The position of the control rack is corrected automatically and constantly while the engine is running;
The device is particularly robust and simple to produce; furthermore it only calls upon production techniques which are well known from the prior art;
The control device in particular envisages that:
The control of the position of the control rack is accurate enough to allow accurate control of the volumetric ratio of the engine;
The accuracy with which the position of the control rack is controlled deteriorates little throughout the life of the engine, and any leaks of hydraulic fluid are automatically and constantly compensated for.
In order to achieve these results, the control device for altering the position of the control rack comprises:
An actuator body mounted so that it is stationary with respect to the engine block parallel to the control rack;
An actuator cover mounted so that it is stationary with respect to the actuator body;
An actuator piston, an actuator rod and an actuator rod extender which are assembled with the control rack, which constitute the upper system for guiding said engine control rack and which can move longitudinally with respect to the actuator body;
A control rod positioned parallel to the actuator rod comprising a shoulder and able to move longitudinally, said control rod passing right through the actuator cover, the actuator body and the actuator piston by virtue of orifices formed in said actuator cover, actuator body and actuator piston;
Valves housed in a duct formed in the mass of the actuator piston, allowing or preventing the flow of hydraulic fluid between the actuator upper and lower chambers as defined by the position of the actuator piston relative to the actuator body;
A nonreturn valve housed in a hydraulic-fluid inlet duct, the orifice of which opens into the central part of the actuator body, said nonreturn valve allowing hydraulic fluid to enter the actuator body but preventing it from leaving this body;
Springs keeping the various valves in contact with their seats;
Sealing devices which may, in a particular embodiment of the invention, consist of rubber O-rings.
According to one particular embodiment, its operation requires one or more low-power slaving mechanisms for altering the longitudinal position of the control rod with respect to the actuator body, taking the dictates of the operation of the engine into account.
The control device for altering the position of the control rack comprises:
An eccentric longitudinal duct which is formed in the mass of the actuator piston and which connects the lower and upper circular surfaces of said actuator piston. The duct is formed in such a way that it constitutes a housing for the two valves which allow or prevent the flow of hydraulic fluid. The duct is of a larger diameter than the valves so as to allow fluid to flow along said duct when said valves are open;
An eccentric longitudinal duct which is formed in the mass of the actuator piston and which provides the control rod with longitudinal guidance;
An actuator piston which has a cavity on its cylindrical surface facing the hydraulic fluid inlet orifice opening into the central part of the actuator body. The cavity has a height at least equivalent to the maximum stroke of the actuator piston and is connected to the eccentric longitudinal duct formed in the mass of the actuator piston;
Valves which allow or prevent the flow of hydraulic fluid between the actuator upper and lower chambers as defined by the position of the actuator piston relative to the actuator body. The valves consist of rings which can slide around the control rod. The inside diameter of the valves is smaller than the diameter of the shoulder of the control rod. When the valves are not held open by the shoulder of the control rod they are held on their seats by springs;
A shoulder on the control rod which centers said control rod in the eccentric longitudinal duct formed in the mass of the actuator piston. The shoulder allows one or other of the valves which allow or prevent the flow of hydraulic fluid between the actuator upper and lower chambers to be moved. The shoulder is provided with grooves or slots to allow fluid to flow along the duct;
A nonreturn valve which is housed in the hydraulic-fluid inlet duct, the orifice of which opens into the central part of the actuator body and which, according to one particular embodiment, may consist of a ball held on a seating surface by a spring and closing an orifice;
A hydraulic-fluid inlet duct, the orifice of which opens into the central part of the actuator body and which, according to a particular embodiment, may be connected to the pressurized hydraulic circuit which lubricates the variable-displacement engine.
The device according to the invention for allowing the effective volumetric displacement and/or the effective volumetric ratio of a piston engine to be varied while it is running comprises:
A first device for controlling the volumetric ratio of the engine by modifying the starting point of the stroke of the piston with respect to the cylinder without modifying the length of said stroke;
And a second device allowing the effective volumetric displacement of the engine to be controlled by discharging into the inlet pipe excess gases let into the cylinder of the engine and by adjusting the length of the piston upstroke used for compressing the gases.
The device according to the present invention comprises a first device for controlling the volumetric ratio of the engine, which consists of a system of gears which comprises:
A rack integral with the lower part of the piston and which is held in a guide system allowing said rack a longitudinal translational movement;
A control rack guided in longitudinal translation in the engine block;
A device for controlling the position of the control rack;
And a gear mounted freely on a connecting rod which is also free on a crankshaft so that the gear is positioned between the two racks to form the element which transmits movement between the piston and the connecting rod.
The device according to the present invention comprises a second device controlling the effective volumetric displacement of the engine consisting of an additional inlet valve and of a device which controls its opening/closure and which allows the angular offset of the point at which said valve opens and closes with respect to the crankshaft to be modified.
The device according to the present invention comprises a second device for controlling the effective volumetric displacement of the engine, without an additional inlet valve, consisting of a device which controls the opening and closure of an inlet valve known per se and which allows the angular offset of the point at which said valve closes and opens with respect to the crankshaft to be modified.
The device according to the present invention comprises a device controlling the opening and closure of the additional inlet valve which is a camshaft slaved to a device which controls its angular offset with respect to the engine crankshaft.
The device according to the present invention comprises a device controlling the opening and closure of the inlet valve known per se which consists of an additional camshaft slaved to a device which controls its angular offset with respect to the engine crankshaft, said additional camshaft operating said valve via a mechanical linkage which is in addition to the movement imparted to said valve by its camshaft.
The device according to the present invention comprises a device controlling the angular offset of the camshaft controlling the opening of the additional inlet valve which consists of an intermediate pulley, the position of which defines the length of the timing belt or chain between the pulley of the camshaft for the engine inlet valves and exhaust valves and the pulley of the camshaft which opens the additional inlet valve.
The device according to the present invention comprises a device controlling the position of the control rack which consisting of a hydraulic actuator which acts on said rack via a mechanical linkage.
The device according to the present invention comprises a device which controls the position of the intermediate pulley consisting of a hydraulic actuator.
The device according to the present invention comprises a gear which has a truncated profile so that it retains only those teeth which will be useful in transmitting movement between the piston and the connecting rod.
The device according to the present invention comprises bearing surfaces which are formed respectively the gear and the racks to allow said gear to be constantly centered between said racks, while the point of contact between said bearing surfaces is constantly positioned at the pitch-circle diameter of the gear.
The device according to the present invention comprises a piston, the cylindrical part of which is tall enough to house piston rings but has no skirt for its longitudinal guidance.
The device for varying the effective volumetric displacement and/or the effective volumetric ratio of a piston engine comprises a device for controlling the position of the control rack which comprises:
A hydraulic actuator comprising means for extending its rod allowing it to maintain a volume of fluid displaced as a function of the stroke of the actuator piston which is identical for each of the chambersxe2x80x94upper and lowerxe2x80x94of said actuator.
Control mechanisms which allow the rod of the actuator to be displaced into a determined position or kept in a determined position with respect to the body of the actuator.
The device according to the present invention comprises a control device which comprises:
An actuator body mounted so that it is stationary with respect to the engine block, parallel to the control rack, an actuator cover mounted so that it is stationary with respect to the actuator body, an actuator piston, an actuator rod and an actuator rod extender which are assembled with the control rack, which constitute the upper system for guiding said control rack and which can move longitudinally with respect to the actuator body,
Control mechanisms which consist of a control rod which has a shoulder and which can move longitudinally, said control rod being positioned parallel to the actuator rod and passing right through the actuator cover, the actuator body and the actuator piston via orifices formed in said actuator cover, actuator body and actuator piston, of valves housed in a duct placed longitudinally and eccentrically and formed in the mass of the actuator piston, said valves allowing or preventing the flow of hydraulic fluid between the actuator upper and lower chambers as defined by the position of the actuator piston relative to the actuator body, said valves consisting of rings which can slide around the control rod, and their inside diameter being smaller than the diameter of the shoulder of the control rod so that it is possible to hold them open using said shoulder of said control rod, when said valves are not held open by said shoulder of said control rod, they are kept on their seats by springs and a nonreturn valve which is housed in a hydraulic-fluid inlet duct, the orifice of which opens into the central part of the actuator body, said nonreturn valve allowing hydraulic fluid to enter the actuator body but preventing it from leaving this body.
The device according to the present invention comprises a control device which comprises an actuator piston which has a cavity on its cylindrical surface facing the orifice of the hydraulic-fluid inlet duct opening into the central part of the actuator body, said cavity being of a height at least equivalent to the maximum stroke of said actuator piston and being connected to the duct placed longitudinally and eccentrically and formed in the mass of said actuator piston connecting the upper and lower circular surfaces of said actuator piston, via a connecting passage.
The device according to the present invention comprises a control device which comprises a nonreturn valve consisting of a ball held on a seating surface by a spring and closing an orifice.
The device according to the present invention comprises a control device which comprises a hydraulic-fluid inlet duct, one of the orifices of which opens into the central part of the actuator body and which is connected to the pressurized hydraulic circuit which lubricates the variable-displacement engine.
The device according to the present invention comprises a control device which comprises sealing elements consisting of rubber O-ring seals.
The device according to the present invention comprises a control device in which the shoulder centers the control rod in the duct placed longitudinally and eccentrically and formed in the mass of said actuator piston, said shoulder having grooves or slots to allow fluid to flow along said duct.
Other characteristics and advantages of the present invention will become clearer from reading the description which will follow, given in conjunction with the appended drawings.